PHOTOCHEMICAL E-REVERSIBLE-ARROW-Z ISOMERIZATION OF SOME BENZYLIDENE CAMPHOR AND BENZYLIDENE TETRAHYDROFURANONE DERIVATIVES

The E reversible arrow Z photoisomerization of benzylidene camphor and benzylidene tetrahydrofuranone was examined in various solvents. The isomerization quantum yields determined from different methods were fo und to be independent of the concentration and of the irradiation wave length. No solvent and oxygen effects were observed on this quantum yi eld. The kinetic constants of the thermal Z reversible arrow E isomeri zation at 30 degrees C were calculated. A marked role of protic solven t on the reaction rate was found with the hydroxylated derivatives. Th e measured quantum yield of the irreversible phototransformation depen ds on the nature of the aromatic ring substituents and of the hydrogen -donor character of the solvent.